This invention relates generally to scintillator single crystals and, more particularly, to a scintillator single crystal that operates at a high temperature and detects a high-energy radiation.
There is currently a need for gamma ray detection in the oil well drilling industry. Gross gamma-ray counting is normally used for log depth matching and as shale/sand contrast indicator. Gamma-ray detectors may also be used to derive lithology, porosity, and permeability indicating the location, volume and ease of extraction of the oil. A small, robust sensor capable of detecting such rays is highly desirable and necessary for harsh, down-hole environments where shock levels are more than 20 root mean square acceleration (Grms) and temperatures may vary widely from below room temperature to exceeding 175° Celsius (C).
Several current technologies utilize gamma sensors that include photomultiplier tubes (PMTs) spectrally matched to scintillators. The scintillators emit UV or blue light when excited by a high energy radiation such as gamma radiation, and the PMTs are used to transform UV or blue light signals to readable level electronic signals. However, life time of the PMTs considerably reduce at high temperatures. Hence, the lifetimes of PMTs may become prohibitively short, thereby driving up the cost of their use sharply. Further, PMTs often require high operating voltages and are also fragile and prone to failure when vibration levels are high. Usage of solid state avalanche photodiode (APD)s instead of PMTs for the detection of high-energy radiation is desirable at these conditions.
Solid state avalanche photodiodes may have different spectral profile than the PMTs, and the scintillators that operate with the solid state APDs are desirable to be spectrally matched to the APDs. Gamma-ray peak resolving capacity of the currently used scintillator of alkaline halide crystal activated by tellurium ion degrades significantly at temperature>175° C. Orthosilicates of lutetium and yttrium were earlier used as scintillator materials. However, these orthosilicates were found to be not having high-temperature stable emission properties. Praseodymium doped lutetium pyrosilicate scintillator were studied for positron emission tomography (PET) application. However, lutetium, lanthanum, gadolinium, and rubidium are known to have inherent gamma ray emission and hence may not be best to be used for the detection of high-energy radiation detection including gamma radiation.
Therefore, there is an existing need to have apparatus and methods that operate at a wide variety of temperature levels including at temperatures as high as or higher than 175° C., for detecting high energy radiation without much deterioration of the detected signals.